The present invention relates to a laundry washing machine with an electronic device for sensing the motion of the wash assembly due to the dynamic unbalance of the wash laundry drum assembly, and to the relative operating method.
More specifically, the present invention relates to a home laundry washing machine or combination washing machine-drier equipped with a device for evaluating a dynamic unbalance parameter related to the torque and speed acting on the wash assembly of the machine as a result of dynamic unbalance effects, and for accordingly activating or not the spin stage; to which the following description refers purely by way of example.
Home washing machines are known to comprise a casing, a laundry wash assembly comprising a cylindrical tub connected in floating manner to casing by suspension devices, a laundry drum mounted inside the tub to rotate freely about a longitudinal axis of rotation; and an electric motor connected mechanically to laundry drum by a transmission system to rotate laundry drum about longitudinal axis of rotation inside tub.
It is important to point out that the term “laundry drum assembly” will be intended to mean the assembly comprising the laundry drum, the laundry arranged into the laundry drum, and all the rotating parts of a transmission system used to impress the rotating motion to the laundry drum, i.e. pulleys, transmission shafts, and rotor of the electric motor.
In addition home washing machines comprises electronic control devices for measuring a physical parameter related to unbalance of the laundry drum assembly caused by random distribution of the laundry inside the laundry drum of the wash assembly, and accordingly determining potentially critical overall unbalance of the laundry drum assembly.
The main purpose of such devices is to achieve a predetermined spin speed of the laundry drum inside the wash assembly without producing unbalance of the laundry drum assembly over and above a maximum permissible threshold, which poses various problems in the machine, such as: collision of the wash assembly with the machine casing, and/or severe vibration resulting in a high noise level, and/or partial deformation of the laundry drum, and/or mechanical stress of the drum supporting members, i.e. bearings, dampers, springs, inside the wash assembly.
Unbalance of the laundry drum assembly of a washing machine caused by random distribution of the laundry inside the laundry drum can be divided substantially into two unbalance components, each associated with a respective distribution pattern of the laundry inside the laundry drum, and with a given rotation of the laundry drum caused by the distribution pattern.
More specifically, a first theoretical unbalance component—known as static unbalance and shown in the FIG. 1 example—is represented by a first static mass MS distribution pattern, in which the static mass MS is concentrated at one point on the inner wall of a laundry drum T.
More specifically, in the first distribution pattern, mass MS is located inside laundry drum T with its barycentre BMS aligned vertically with the barycentre BTS of wash assembly; and, as laundry drum T rotates, the first theoretical distribution pattern of static mass MS produces a substantially cylindrical rotation C (shown by the dash line) of the longitudinal axis L of laundry drum T with respect to its rest position. In other words, the cylindrical component of rotation of longitudinal axis L of laundry drum T is mainly associated with the “static unbalance” component of the laundry.
The second unbalance component—known as “dynamic unbalance” (shown schematically in FIG. 2)—is associated with a second laundry distribution pattern represented by two masses MAD and MPD, which are equal in weight, and are located opposite each other with respect to a vertical axis through the barycentre BTD of wash assembly; and, as laundry drum T rotates, the distribution pattern of the two masses MAD and MPD produces a substantially conical rotation of longitudinal axis L with respect to its rest position. In this case, projection of the rotation of longitudinal axis L in a plane perpendicular to longitudinal axis L in non-rotation conditions is defined by an ellipse E (shown by a dash line in FIG. 2).
In other words, the conical component of rotation of longitudinal axis L of laundry drum T with respect to its rest position is mainly associated with the “dynamic unbalance” component of the laundry.
Though efficient, known control devices have the major drawback of determining unbalance of the laundry drum assembly solely on the basis of “static unbalance” as described above, i.e. associated solely with the “cylindrical component” of rotation of the longitudinal axis of the laundry drum assembly (FIG. 1), and of failing to determine the “dynamic unbalance”, i.e. “conical” unbalance component (FIG. 2).
Known control devices, in fact, determine unbalance of the laundry drum assembly by processing the fluctuation in speed or torque acting in the wash assembly and imparted by its electric drive motor for regulating the rotating speed. Fluctuation in speed or torque, however, is related mainly to static unbalance, and provides no useful information concerning dynamic unbalance, which, being produced by a distribution pattern defined by two opposite masses of equal weight, produces weak fluctuation in the speed or torque imparted to the laundry drum assembly by the electric motor and therefore it cannot be determined using known control devices of the type described above.